Coronavirus morphology and evolution, with special emphasis on coronaviruses of carnivores

The several studies carried out by different researchers on canine coronavirus (CCoV) have focused upon the epidemiological relevance of this virus and, considering the wide diffusion of CCoV infections among dog populations, the Author underlines the need for further investigation on the biology of CCoVs and on the pathogenetic role of their infections. Genetic diversity among coronaviruses is accounted for by linear evolution as well as by a sudden, dramatic shift generated by RNA deletion or recombination events. In the last decade it has been observed that CCoV has evolved. During the monitoring of two pups naturally infected with CCoV, a long-term faecal shedding of the virus was observed and sequence analysis of the M gene fragment amplified from the faecal samples collected in the late stage of the CCoV infection, revealed a genetic drift to FCoV, which has led to the designation of these atypical CCoVs as FCoV-like CCoVs. In order to investigate more in-deeply the genetic diversity of these FCoV-like CCoVs, the attention was focused on the S gene which possesses a high degree of variation in the 5’end whereas it is more conserved in the 3’end. The analysis confirmed the existence of a new CCoV genotype in the faeces of pups with enteritis, which has been referred to as CCoV type I